Slipper sole



FIG. 1 is a perspective view of a slipper sole, showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top plain view thereof; and,

FIG. 7 is a bottom plain view thereof.

The broken lines illustrate environmental structure and form no part of the claimed design. 

The ornamental design for a slipper sole, as shown and described. 